Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-10-06
2002-07-09
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000, C349S111000
Reexamination Certificate
active
06417901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device for use in a direct-view display, a projection display and the like.
2. Description of the Related Art
In recent years, the size and weight of office automation apparatuses such as a personal computer have been reduced, and portable information apparatuses which are usually carried by persons have been put into a practical use. As a display unit for such information apparatuses, a liquid crystal display (LCD) device using liquid crystal has been used most widely because of low power consumption, small size and light weight. As such a liquid crystal display device, a transmission type liquid crystal display device using a back light is usually utilized. In recent years, low power consumption displays have been required and a reflection type liquid crystal display device using no back light has been developed vigorously.
As an example of conventional reflection type liquid crystal display device, a reflection type liquid crystal display device disclosed in Japanese Unexamined Patent Publication JP-A 5-323371 (1993) will be described below.
FIG. 15
is a plan view showing a conventional reflection type liquid crystal display device, and
FIG. 16
is a sectional view taken along line A—A of the LCD device shown in
FIG. 15. A
plurality of scanning lines
102
formed of a material such as aluminum, tantalum or the like are disposed in parallel with each other on an insulating substrate
101
made of glass or the like. A gate electrode
103
branches off from each of the scanning lines
102
. A gate insulating film
104
made of nitride silicon (SiN
x
), silicon oxide (SiO
2
) or the like is disposed over the whole substrate
101
to cover the gate electrode
103
. A semiconductor active layer
105
made of amorphous silicon, polycrystalline silicon or the like is disposed on the gate insulating film
104
provided on the gate electrode
103
. A contact electrode
106
made of amorphous silicon to which impurity ions are added, microcrystal silicon, polycrystalline silicon or the like is disposed on both ends of the semiconductor active layer
105
. A source electrode
107
and a drain electrode
108
which are made of aluminum, titanium, tantalum, chromium or the like are disposed on the contact electrodes
106
formed on the both ends.
As shown in
FIG. 16
, a signal line
110
intersecting with the scanning line
102
with the gate insulating film
104
interposed therebetween is connected to the source electrode
107
. The signal line
110
is also formed of the same material as the material of the source electrode
7
. The gate electrode
103
, the gate insulating film
104
, the semiconductor active layer
105
, the contact electrode
106
, the source electrode
107
and the drain electrode
108
constitute a thin film transistor (TFT)
111
. The TFT
111
has the function of a switching element.
An interlayer insulating film
112
comprising an inorganic material such as nitride silicon or an organic material is formed over the whole substrate
101
to cover the scanning line
102
, the signal line
110
and the TFT
111
. A pixel electrode
113
comprising a material having a high reflectivity such as Al is formed on the interlayer insulating film
112
. A contact hole
114
is formed in a portion of the interlayer insulating film
112
which overlaps with the drain electrode
108
. The pixel electrode
113
and the drain electrode
108
are connected to each other through the contact hole
114
. Furthermore, an orientation film (not shown) is formed on the pixel electrode
113
. Thus, an active matrix substrate portion is formed.
An opposite substrate portion is disposed to be opposite to the active matrix substrate portion. In the opposite substrate portion, a color filter
116
is formed on an insulating substrate
115
made of glass or the like. One of red, green and blue color layers
116
R,
116
G and
116
B is formed in a region of the color filter
116
corresponding to the pixel electrode
113
, and a metallic shielding film (black matrix)
116
BM made of chromium nitride, tantalum nitride or the like is disposed in a region opposite to a region between the pixel electrodes
113
or to the signal line
110
. The black matrix is formed of black resin and the like other than metals. A common electrode
117
comprising a transparent conductive material such as ITO is formed on the color filter
116
. A liquid crystal layer
118
is provided between the active matrix substrate portion and the opposite substrate portion.
Next, the operation of a reflection type liquid crystal display device having such a structure will be described. When the TFT
111
is turned on, a current flows from the signal line
110
to the pixel electrode
113
and the pixel electrode
113
is charged to the voltage of the signal line
110
obtained at that time. At this time, a voltage is applied to the liquid crystal layer
118
interposed between the pixel electrode
113
and the common electrode
117
so that the liquid crystal layer
118
operates. In the reflection type liquid crystal display device, light incident from the opposite substrate portion side is reflected by the pixel electrode
13
, thereby performing display. The light incident from the opposite substrate portion side is reflected by the pixel electrode
113
and polarized by the liquid crystal layer
118
so that the transmittances of pixels differ from each other. Consequently, a contrast is formed between two or more pixel electrodes
113
and image display is accomplished.
On the insulating substrate
115
of the opposite substrate portion is formed the color filter
116
, in which the black matrix
116
BM is formed in a region of the insulating substrate to be opposite to a region between the pixel electrodes
113
or to the signal line
110
. In order to reduce the cost of the color filter, a structure free from the black matrix
116
BM (which will be hereinafter referred to as a BM-less structure) has been examined. This is because there is a problem that the manufacturing cost is greatly increased in the case of use of a metal film for the black matrix. A possible BM-less structure will be described with reference to FIG.
17
.
(1) As shown in
FIG. 17A
, no black matrix is formed in a region of the insulating substrate
115
, opposite to a region between the pixel electrodes
113
or to the signal line
110
, and the common electrode
117
and the orientation film
151
are directly disposed on the insulating substrate
115
.
(2) As shown in
FIG. 17B
, in the region opposite to the region between the pixel electrodes
113
or to the signal line
110
are overlapped the red color layer
116
R and the green color layer
116
G, on which the common electrode
117
and the orientation film
151
are laminated.
Alternatively, the red color layer
116
R and the green color layer
116
G may be disposed to be adjacent leaving no interval therebetween in the region opposite to the region between the pixel electrodes or to the signal line and the scanning line, instead of overlapping the color layers of the color filter. By overlapping the color layers of the color filter or arranging the color layers to be closely adjacent, light can be more shielded than in the examples of FIG.
17
A and
FIG. 17C
, which will be described below.
(3) As shown in
FIG. 17C
, an insulating film
152
is formed on the color filter
116
to be flat. In that case, the insulating film
152
is embedded in the region opposite to the region between the pixel electrodes
113
or to the signal line
110
. The common electrode
117
and the orientation film
151
are provided on the insulating film
152
.
With the structures shown in
FIGS. 17A
to
17
C, shielding properties are more deteriorated than in the structure having the black matrix. Therefore, light transmission occurs in the region opposite to the region between the pixel electrodes
113
or to the signal line
110
. In the case where the prior art reflection type liqui
Ban Atsushi
Murai Atsuhito
Okada Yoshihiro
Sato Takashi
Nixon & Vanderhye P.C.
Qi Mike
Sharp Kabushiki Kaisha
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